Air < Fat < Fluid < Bone < Metal

(In order of increasing brightness)

• Right Patient
• Right Date
• Any old X-Rays for comparison

Is there evidence of Rotation?

Look at the medial aspect of clavicles.  Should be equidistant to the superimposed spinous process

Is there evidence of Inspiratory Effort?

How many ribs do we see

9 ribs minimum for a good inspiratory effort

How is the Penetration?

Over penetrated = black

Under penetrated = white

What Technique was used?

PA vs. AP

Search Pattern

Start at the center and work your way to the edges

Always compare one side to the other

• Posterioranterior View (PA)
• Anteriorposterior View (AP)
• Lateral View
• Decubitus View

• Usually more preferred
• The closer an object to the film, the sharper the borders
• Most of the important structures in the chest are located anteriorly
• Radiograph shot from the patient's back, with their chest placed against the film

• Done when the patient is too sick to stand for the PA view
• "Portable" CXR
• Radiograph is shot from the patients front, with the film placed behind the patients back
• Heart is farther from the film, and therefore appears larger

• Taken with the patient in profile
• Taken routinely with the PA view to localize lung lesions, which may be hidden behind the heart or the diaphragm

• Radiograph taken with the patient lying on their side
• Useful to identify fluid in the pleural space
• Fluid is heavier than air and gravity will therefore cause it to collect in the lowest portion of the chest

• Contains several important structures including the heart, great vessels, the trachea, main-stem bronchi, the esophagus and innumerable lymph node
• The mediastinum connects with each lung via a bridge-like structure called the hilum

Right lungs composed of 3 lobes

Left lungs composed of 2 lobes

Lingula: the tongue-like portion of the left upper lobe that "licks" the left heart border

Lobes are separated from each other by fissures

In the right lung

• Horizontal fissure separates the middle lobe from the upper
• Oblique fissure separates the lower lobe from the middle

In the left lung

• A single oblique fissure separates the 2 lobes

Costophrenic angles or Sulci

• Name given to the spaces caused by the parietal pleura reflecting deep into the recesses made by the diaphragm and the chest wall

• Composed of the right and left hemi-diaphragm
• Right hemi-diaphragm sits higher due to the presence of the liver
• On the lateral view, the heart sits on the left hemi-diaphragm, which helps differentiate it from the right

• Innumerable thin white lines randomly distributed in the lungs
• This pattern represents the presence of a fluid density in the lungs

• An area of lung takes on a honeycomb appearance
• Signifies longstanding interstitial lung disease and irreversible scarring (asbestosis)

• Innumerable pellet sized white dots appearing diffusely in both lungs
• Often seen in Miliary TB

• If a water density process in the lung such as a pneumonia is next to another water density structure such as the heart, the border between them is lost
• There is no border between the same two density structures in anatomical contact

Silhouette Sign: Commonly obliterated borders

• Right heart border = RML Pneumonia
• Left heart border = Lingula Pneumonia (LUL)
• Right hemi-diaphragm = RLL Pneumonia
• Left hemi-diaphragm = LLL Pneumonia
• Descending Aorta = LLL Pneumonia

• Small horizontal lines seen in the periphery of the lung
• These lines are water density and always extend to the pleura
• Seen in states where there is increased fluid density material in the interlobular septa

• Used to determine whether a mass or nodule arises from the lung or from a surrounding structure
• Picture throwing a snowball at the lung wall...if the mass looks like a snowball just before the impact, it is localized in the lung. 
• If it looks like a flattened snowball after impact, it arises from a surrounding structure (i.e. chest wall, pleura, mediastium) 

• Blood leaking from the aortic collects near the aortic arch.  The mediastinal pleural and fat attempt to contain the hematoma, which becomes round and localized
• On CXR, look for

1. Mediastinum may appear white (>8cm)
2. Aortic arch becomes blurred
3. There may be blood over the apex of a lung appearing as a white crescent cap (apical cap)
4. The hematoma pushes the trachea to the right and left mainstem bronchus downward
5. NG tube, if present may be pushed to the right

• Mediastinal air appears as black streaks on the radiograph
• The air may outline mediastinal structures
• Indicative to an injury involving the lungs, esophagus or trachea
• Also, remember that the mediastinum is connected to the retroperitoneum and that retroperitineal air such as a bowel perforation can track up into the mediastinum

• If the heart's largest transverse measurement is greater than half the width of the chest, there is an enlarged cardiac silhouette
• Seen in cardiomegaly, CHF, cardiomyopathy, and pericardial effusions

Pneumonia: TOO WHITE

• Focal Air Disease

• May involve part or all of a lobe
• Often caused by bacterial infection
• May see a Silhouette sign or air bronchogram sign

Pneumonia: TOO WHITE

• Diffuse Interstitial

• Primarily an infection of the interstitium of the lung
• Usually bilateral and appears as multiple white lines
• Mainly caused by viruses and mycoplasma

Pneumonia: TOO WHITE

• Tuberculosis

• Primary infection usually results in airspace disease of the lower lobes, pleural effusions and hilar lymph node enlargement
• Secondary infection tends to occur in the upper lobes.  The involved lung often forms a cavity and scar tissue

• The innumerable alveoli that make up the lungs are analogous to air filled balloons.  If for some reason air is resorbed from a significant portion of these structures, there will be loss of colume or collapse of the affected area (atalectasis)
• Since the alveoli no longer contain air, the affected air will appear as white on a radiograph

• Appears as a thick white soft tissue density ring with a dark air center
• Often are partially filled with fluid, giving rise to the appearance of air/fluid level
• Often caused by:

1. Abscess
2. Fungal Pneumonia
3. Granulomatous diseases such as TB
4. Tumors

• Pleural effusion is a collection of pus between the visceral and parietal pleura (pleural space)
• Fluid may be

1. serous (pleural effusion)
2. blood (hemothorax)
3. pus (empyema)

• Radiograph technique is important in diagnosis

(i.e. upright vs. supine vs decubitus views)

• Occurs when the heart is not able to pump out the same amount of blood it is receiving
• The heart becomes enlarged (cardiomegaly)
• In left sided heart failure, fluid backs up in the pulmonary veins and lung
• Fluid seeps out into the interstitium first and then eventually into the alveoli and pleural space

On radiograph, look for the following findings

• Vascular Redistribution (Blood vessels in the upper lung zones become larger than the ones in the lower lung zones)
• Interstitial Pattern and Kerly B lines
• Peribronchial Cuffing (Bronchi seen head on surrounded by fluid)
• Pleural Effusions
• Batwing Pattern (Symmetrical airspace disease in the lung adjacent to the hila)
• Cardiomegaly

• If an abnormal white area has not changed when compared to previous exam, there is like CHRONIC lung disease
• Honeycomb pattern is suggestive of scarring

• Appear as white, round fluid density lesions
• Nodule = < 3 cm
• Mass = > 3 cm
• Can be caused by both benign and malignant processes
• Further testing is required

• Air between the parietal and visceral pleura, usually arising from lung injury
• Remember air has a tendency to rise to the highest point in the lung, in contrast to fluid
• On an upright radiograph, look for a black crescent over the apex of the lung
• The visceral pleura is often seen as a thin, white line under the black crescent since it is flanked by air on either side. You should not be able to see branching white vessels peripheral to this line
• Taking a radiograph during expiration often makes a pneumonthorax more visible because the amount of pleural air remains the same although the lungs become smaller
• Deep Sulci sign: On supine radiographs, air rises to the anterior and lateral costophrenic angles.  This is because they are the highest regions in the pleural cavity when the patient is lying supine.  This makes the lateral sulcus abnormally dark and deep.

• Caused by chronic airway obstruction resulting in destruction of the alveoli
• Lungs contain more air than normal because the airway obstruction causes air trapping
• Sometimes ball shaped collections of air develop, called bullae
• Radiographic findings include:

1. An overall decrease in lung density (too black appearance)
2. Flattening of the diaphragm because of hyperinflation of the lungs

• Most common findings is a normal (or close to normal) chest radiograph
• Sometimes a focal black wedge shaped area is seen, as blood does not fill the vessel areas distal to the embolism
• Nonspecific signs include

1. Atelectasis and pleural effusion
2. Hampton's Hump = white wedge shaped area of air space disease, seen due to post-obstruction infarction

• Rib Fracture
• Subcutaneous Emphysema

1. Refers to air under the skin, either in the chaest wall or the neck
2. Observed as dark air density streaks in the soft tissue

• Rupture

1. Caused by significant trauma and occurs on the left side 9 of 10 times
2. Abnormal structures may herniate through the tare
3. On radiographs

• The affected hernia diaphragm may be elevated
• There may be an air-fluid level, implying presence of bowel in the chest
• Displacement of the mediastinum away from the tare
• NG tube tip may appear in the chest

• Hiatal Hernia

1. Slippage of the top part of the stomach into the mediastinum through the esophageal hiatus of the diaphragm
2. The gastric fundus may appear as fluid density mass, or an air-fluid level, behind the heart

A = Air Spaces

• Gastric Bubble

Seen in LUQ, little to no clinical significance

• Free Air

1. Usually seen between the liver and the diaphragm
2. A thin line would appear in the RUQ suggesting free air isolating the diaphragm
3. Seen on upright radiograph

• Lung Spaces

1. Start your inspection at the patient's jaw and inspect side to side for any abnormalities.  Look for areas disproportionately too black or too white when compared to the rest of the radiographs

B = Bones and Borders

• Look for the bones of the radiograph
• Start at the right clavicle, inspect the humerus, the head of the humerus, the glenoid process, all the bones on the right.  Look at the right acromioclavicular joint.  Trace every single rib on the right.  Inspect the vertebral bodies for compression fractures or other abnormalities.  Any lytic lesions?
• Do the same for left side

C = Cardiovascular and Mediastinum

• Inspect the heart size for an enlarged cardiac silhouette
• Determine the cardiothoracic ratio

1. The measure distance from the right side of the heart to the left side of the heart
2. If the hearts largest transverse measurement is greater than half the width of the chest, there is an enlarged cardiac silhouette
3. If the patient has pericardial effusion, it may falsely make the heart appear larger than it actually is.  If this is suspected, do a bedside ultrasound or formal echodiagram

• Inspect the mediastinum...is it TOO wide

1. > 8 cm or 80 mm
2. Pager sign
3. Suspect thoracic aneurysm when widened

S = Soft Tissue

Look at the neck, breast tissue and external area of the throax for

• Subcutaneous Air
• Tumors
• Foreign Bodies